program laba4x8;
var q:text;
    i,n:byte;
    x:array[1..30] of longint;
begin
assign(q,'input.txt');
reset(q);
readln(q,n);
close(q);
x[1]:=1;
x[2]:=1;
for i:=3 to n do
   x[i]:=x[i-1]+x[i-2];
assign(q,'output.txt');
rewrite(q);
writeln(q,x[n]);
close(q);
end.